Understanding the levels and associated ecological risk caused by heavy metals is important for the sustainable management and utilization of Lake Chilwa catchment, an important ecosystem in Malawi providing fertile lands for agriculture and a designated wetland ratified by the Ramsar convention in 1997. Concentrations of chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), arsenic (As), mercury (Hg) and cadmium (Cd) were analyzed from 22 soil sampling locations. Extraction and quantification were achieved by microwave digestion and Inductively Coupled Plasma Optical Emission Spectrometer, respectively. Mean values were detected in the following order; Zn > Cr > Ni > Cu > Pb > As. Strong correlations were observed between As and Pb (r = 0.85), Cr and Ni (r = 0.82), Cu and Ni (r = 0.81), Cr and Cu (r = 0.8), and Pb and Zn (r = 0.73) suggesting similar sources of input. Principal component analysis revealed that Cu, Pb, Zn and As originate from anthropogenic activities, while Cr and Ni were geogenic. The ecological risk caused by these metals, calculated by the Ecological Risk Index (RI) method, showed a low to moderate ecological risk. The wetland areas had higher overall concentrations and RI values compared to the rest of the catchment. It is therefore important to enforce measures to manage and control these levels to avoid their damaging effects.
Groundwater sources provide an important supply of alternative drinking water in most urban areas in Malawi. This study was conducted to assess the quality of groundwater in Area 25, a typical urban residential area in Malawi. Samples were collected from wells and analyzed for physicochemical and bacteriological parameters following standard methods. Results were compared to Malawi Standards (MS) and World Health Organization (WHO) drinking water quality guidelines. The overall water quality index was computed to ascertain the general quality of the water. Levels of pH, phosphate, sulfate, arsenic, lead, and potassium were below the guideline limits while, electrical conductivity, total dissolved solids, chloride, fluoride, nitrate, total hardness, calcium, and magnesium were observed above permissible limits, posing a health risk to the residents. The quality index ranged from 22 (excellent quality) to 64 (Poor quality) with an average of 41 (good quality). Fecal coliforms were present in 70% of the sampled locations with an average of 7.9 cfu/100 ml. The presence of these bacteria presents a serious risk for waterborne disease outbreaks. This study, therefore, recommends the provision of basic treatment techniques to improve the quality of water in the area before consumption, regular monitoring of groundwater resources, and proper design and setting of septic systems.
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